diff --git a/ivtest/gold/sv_interface_port_forwarding_restrict_fail-iverilog-stderr.gold b/ivtest/gold/sv_interface_port_forwarding_restrict_fail-iverilog-stderr.gold
index 05a2a50ec..90758da05 100644
--- a/ivtest/gold/sv_interface_port_forwarding_restrict_fail-iverilog-stderr.gold
+++ b/ivtest/gold/sv_interface_port_forwarding_restrict_fail-iverilog-stderr.gold
@@ -1,3 +1,3 @@
-ivltests/sv_interface_port_forwarding_restrict_fail.v:30: error: Interface member `hidden' is not listed in modport `consumer'.
-ivltests/sv_interface_port_forwarding_restrict_fail.v:30: error: Unable to elaborate r-value: bus.hidden
+ivltests/sv_interface_port_forwarding_restrict_fail.v:23: error: Interface member `hidden' is not listed in modport `consumer'.
+ivltests/sv_interface_port_forwarding_restrict_fail.v:23: error: Unable to elaborate r-value: bus.hidden
 2 error(s) during elaboration.
diff --git a/ivtest/gold/sv_interface_port_missing_type_fail-iverilog-stderr.gold b/ivtest/gold/sv_interface_port_missing_type_fail-iverilog-stderr.gold
new file mode 100644
index 000000000..601207b55
--- /dev/null
+++ b/ivtest/gold/sv_interface_port_missing_type_fail-iverilog-stderr.gold
@@ -0,0 +1,2 @@
+ivltests/sv_interface_port_missing_type_fail.v:7: error: Interface port bus uses unknown interface type `missing_if'.
+1 error(s) during elaboration.
diff --git a/ivtest/gold/sv_interface_port_positional_unconnected_fail-iverilog-stderr.gold b/ivtest/gold/sv_interface_port_positional_unconnected_fail-iverilog-stderr.gold
index 4201c3c5e..8fc0533db 100644
--- a/ivtest/gold/sv_interface_port_positional_unconnected_fail-iverilog-stderr.gold
+++ b/ivtest/gold/sv_interface_port_positional_unconnected_fail-iverilog-stderr.gold
@@ -1,2 +1,2 @@
-ivltests/sv_interface_port_positional_unconnected_fail.v:13: error: Interface port `bus' of module bus_user is not connected.
+ivltests/sv_interface_port_positional_unconnected_fail.v:7: error: Interface port `bus' of module bus_user is not connected.
 Elaboration failed
diff --git a/ivtest/gold/sv_interface_port_unmodported_missing_type_fail-iverilog-stderr.gold b/ivtest/gold/sv_interface_port_unmodported_missing_type_fail-iverilog-stderr.gold
new file mode 100644
index 000000000..24caf2d27
--- /dev/null
+++ b/ivtest/gold/sv_interface_port_unmodported_missing_type_fail-iverilog-stderr.gold
@@ -0,0 +1,2 @@
+ivltests/sv_interface_port_unmodported_missing_type_fail.v:7: error: Interface port bus uses unknown interface type `missing_if'.
+1 error(s) during elaboration.
diff --git a/ivtest/ivltests/sv_interface_port_forwarding.v b/ivtest/ivltests/sv_interface_port_forwarding.v
index 58cd1bc81..9fb52a87b 100644
--- a/ivtest/ivltests/sv_interface_port_forwarding.v
+++ b/ivtest/ivltests/sv_interface_port_forwarding.v
@@ -4,14 +4,6 @@
 // This file is placed into the Public Domain, for any use, without
 // warranty.
 
-interface bus_if ();
-   logic value;
-   logic mirror;
-   logic hidden;
-
-   modport consumer(input value, output mirror);
-endinterface
-
 module test;
    bus_if bus();
 
@@ -39,3 +31,11 @@ module child(
 );
    assign bus.mirror = bus.value;
 endmodule
+
+interface bus_if ();
+   logic value;
+   logic mirror;
+   logic hidden;
+
+   modport consumer(input value, output mirror);
+endinterface
diff --git a/ivtest/ivltests/sv_interface_port_forwarding_restrict_fail.v b/ivtest/ivltests/sv_interface_port_forwarding_restrict_fail.v
index a0fb3ab79..79a1ced9f 100644
--- a/ivtest/ivltests/sv_interface_port_forwarding_restrict_fail.v
+++ b/ivtest/ivltests/sv_interface_port_forwarding_restrict_fail.v
@@ -4,13 +4,6 @@
 // This file is placed into the Public Domain, for any use, without
 // warranty.
 
-interface bus_if ();
-   logic value;
-   logic hidden;
-
-   modport consumer(input value);
-endinterface
-
 module test;
    bus_if bus();
    parent dut(.bus(bus));
@@ -29,3 +22,10 @@ module child(
 
    assign sample = bus.hidden;
 endmodule
+
+interface bus_if ();
+   logic value;
+   logic hidden;
+
+   modport consumer(input value);
+endinterface
diff --git a/ivtest/ivltests/sv_interface_port_missing_type_fail.v b/ivtest/ivltests/sv_interface_port_missing_type_fail.v
new file mode 100644
index 000000000..df1a5a513
--- /dev/null
+++ b/ivtest/ivltests/sv_interface_port_missing_type_fail.v
@@ -0,0 +1,11 @@
+// This tests the diagnostic path for an interface-typed module port
+// whose interface type name is not declared.
+//
+// This file is placed into the Public Domain, for any use, without
+// warranty.
+
+module bus_user(
+   missing_if.consumer bus
+);
+   initial $display("FAILED");
+endmodule
diff --git a/ivtest/ivltests/sv_interface_port_positional.v b/ivtest/ivltests/sv_interface_port_positional.v
index 8b6d47551..d0cb7d057 100644
--- a/ivtest/ivltests/sv_interface_port_positional.v
+++ b/ivtest/ivltests/sv_interface_port_positional.v
@@ -3,13 +3,6 @@
 // This file is placed into the Public Domain, for any use, without
 // warranty.
 
-interface bus_if ();
-   logic value;
-   logic sample;
-
-   modport consumer(input value, output sample);
-endinterface
-
 module test;
    bus_if bus();
 
@@ -31,3 +24,10 @@ module bus_user(
 );
    assign bus.sample = bus.value;
 endmodule
+
+interface bus_if ();
+   logic value;
+   logic sample;
+
+   modport consumer(input value, output sample);
+endinterface
diff --git a/ivtest/ivltests/sv_interface_port_positional_unconnected_fail.v b/ivtest/ivltests/sv_interface_port_positional_unconnected_fail.v
index 90e17871a..5b9627b52 100644
--- a/ivtest/ivltests/sv_interface_port_positional_unconnected_fail.v
+++ b/ivtest/ivltests/sv_interface_port_positional_unconnected_fail.v
@@ -3,12 +3,6 @@
 // This file is placed into the Public Domain, for any use, without
 // warranty.
 
-interface bus_if ();
-   logic value;
-
-   modport consumer(input value);
-endinterface
-
 module test;
    bus_user dut();
 endmodule
@@ -17,3 +11,9 @@ module bus_user(
    bus_if.consumer bus
 );
 endmodule
+
+interface bus_if ();
+   logic value;
+
+   modport consumer(input value);
+endinterface
diff --git a/ivtest/ivltests/sv_interface_port_unmodported_basic.v b/ivtest/ivltests/sv_interface_port_unmodported_basic.v
index aa981cf2f..c8bad7778 100644
--- a/ivtest/ivltests/sv_interface_port_unmodported_basic.v
+++ b/ivtest/ivltests/sv_interface_port_unmodported_basic.v
@@ -4,12 +4,6 @@
 // This file is placed into the Public Domain, for any use, without
 // warranty.
 
-interface bus_if ();
-   logic [7:0] lhs;
-   logic [7:0] rhs;
-   logic [8:0] sum;
-endinterface
-
 module test;
    logic [7:0] lhs;
    logic [7:0] rhs;
@@ -38,3 +32,9 @@ module add_if(
 );
    assign bus.sum = bus.lhs + bus.rhs;
 endmodule
+
+interface bus_if ();
+   logic [7:0] lhs;
+   logic [7:0] rhs;
+   logic [8:0] sum;
+endinterface
diff --git a/ivtest/ivltests/sv_interface_port_unmodported_missing_type_fail.v b/ivtest/ivltests/sv_interface_port_unmodported_missing_type_fail.v
new file mode 100644
index 000000000..b02bb3985
--- /dev/null
+++ b/ivtest/ivltests/sv_interface_port_unmodported_missing_type_fail.v
@@ -0,0 +1,11 @@
+// This tests the diagnostic path for an unmodported interface-typed
+// module port whose interface type name is not declared.
+//
+// This file is placed into the Public Domain, for any use, without
+// warranty.
+
+module bus_user(
+   missing_if bus
+);
+   initial $display("FAILED");
+endmodule
diff --git a/ivtest/ivltests/sv_interface_port_wildcard.v b/ivtest/ivltests/sv_interface_port_wildcard.v
index 693e702ed..e13630fb6 100644
--- a/ivtest/ivltests/sv_interface_port_wildcard.v
+++ b/ivtest/ivltests/sv_interface_port_wildcard.v
@@ -3,13 +3,6 @@
 // This file is placed into the Public Domain, for any use, without
 // warranty.
 
-interface bus_if ();
-   logic value;
-   logic sample;
-
-   modport consumer(input value, output sample);
-endinterface
-
 module test;
    bus_if bus();
 
@@ -31,3 +24,10 @@ module bus_user(
 );
    assign bus.sample = bus.value;
 endmodule
+
+interface bus_if ();
+   logic value;
+   logic sample;
+
+   modport consumer(input value, output sample);
+endinterface
diff --git a/ivtest/regress-vvp.list b/ivtest/regress-vvp.list
index 9fd43c39b..d205e357e 100644
--- a/ivtest/regress-vvp.list
+++ b/ivtest/regress-vvp.list
@@ -270,12 +270,14 @@ sv_foreach9			vvp_tests/sv_foreach9.json
 sv_foreach10			vvp_tests/sv_foreach10.json
 sv_interface			vvp_tests/sv_interface.json
 sv_interface_port_basic		vvp_tests/sv_interface_port_basic.json
+sv_interface_port_missing_type_fail	vvp_tests/sv_interface_port_missing_type_fail.json
 sv_interface_port_missing_modport_fail	vvp_tests/sv_interface_port_missing_modport_fail.json
 sv_interface_port_non_interface_actual_fail	vvp_tests/sv_interface_port_non_interface_actual_fail.json
 sv_interface_port_wrong_type_fail	vvp_tests/sv_interface_port_wrong_type_fail.json
 sv_interface_port_modport_input_write_fail	vvp_tests/sv_interface_port_modport_input_write_fail.json
 sv_interface_port_unlisted_member_fail	vvp_tests/sv_interface_port_unlisted_member_fail.json
 sv_interface_port_unmodported_basic	vvp_tests/sv_interface_port_unmodported_basic.json
+sv_interface_port_unmodported_missing_type_fail	vvp_tests/sv_interface_port_unmodported_missing_type_fail.json
 sv_interface_port_forwarding	vvp_tests/sv_interface_port_forwarding.json
 sv_interface_port_forwarding_restrict_fail	vvp_tests/sv_interface_port_forwarding_restrict_fail.json
 sv_interface_port_positional	vvp_tests/sv_interface_port_positional.json
diff --git a/ivtest/vvp_tests/sv_interface_port_missing_type_fail.json b/ivtest/vvp_tests/sv_interface_port_missing_type_fail.json
new file mode 100644
index 000000000..bc986c918
--- /dev/null
+++ b/ivtest/vvp_tests/sv_interface_port_missing_type_fail.json
@@ -0,0 +1,6 @@
+{
+    "type"          : "CE",
+    "source"        : "sv_interface_port_missing_type_fail.v",
+    "gold"          : "sv_interface_port_missing_type_fail",
+    "iverilog-args" : [ "-g2005-sv" ]
+}
diff --git a/ivtest/vvp_tests/sv_interface_port_unmodported_missing_type_fail.json b/ivtest/vvp_tests/sv_interface_port_unmodported_missing_type_fail.json
new file mode 100644
index 000000000..e35cde0c3
--- /dev/null
+++ b/ivtest/vvp_tests/sv_interface_port_unmodported_missing_type_fail.json
@@ -0,0 +1,6 @@
+{
+    "type"          : "CE",
+    "source"        : "sv_interface_port_unmodported_missing_type_fail.v",
+    "gold"          : "sv_interface_port_unmodported_missing_type_fail",
+    "iverilog-args" : [ "-g2005-sv" ]
+}
diff --git a/lexor.lex b/lexor.lex
index 97e07560c..0e0c2646c 100644
--- a/lexor.lex
+++ b/lexor.lex
@@ -120,6 +120,8 @@ static list<int> keyword_mask_stack;
 static int comment_enter;
 static bool in_module = false;
 static bool in_UDP = false;
+static bool in_module_port_list = false;
+static bool module_port_list_start = false;
 bool in_celldefine = false;
 UCDriveType uc_drive = UCD_NONE;
 static int ts_state = 0;
@@ -139,6 +141,12 @@ void lex_in_package_scope(PPackage*pkg)
       in_package_scope = pkg;
 }
 
+void lex_in_module_port_list(bool flag)
+{
+      in_module_port_list = flag;
+      module_port_list_start = flag;
+}
+
 %}
 
 %x CCOMMENT
@@ -160,6 +168,7 @@ void lex_in_package_scope(PPackage*pkg)
 %x REAL_SCALE
 
 W [ \t\b\f\r]+
+ID [a-zA-Z_][a-zA-Z0-9$_]*
 
 S [afpnumkKMGT]
 
@@ -335,7 +344,7 @@ TU [munpf]
 <EDGES>"z0" { return K_edge_descriptor; }
 <EDGES>"z1" { return K_edge_descriptor; }
 
-[a-zA-Z_][a-zA-Z0-9$_]* {
+{ID} {
       int rc = lexor_keyword_code(yytext, yyleng);
       switch (rc) {
 	  case IDENTIFIER:
@@ -434,6 +443,22 @@ TU [munpf]
 	    }
       }
 
+      if (rc == IDENTIFIER && gn_system_verilog() &&
+	  in_module_port_list && module_port_list_start) {
+	    char save_ch = *yy_c_buf_p;
+	    *yy_c_buf_p = yy_hold_char;
+	    const char*cp = yy_c_buf_p;
+	    while (*cp == ' ' || *cp == '\t' || *cp == '\b' ||
+		   *cp == '\f' || *cp == '\r' || *cp == '\n')
+		  cp += 1;
+	    if (*cp == '.' || isalpha(static_cast<unsigned char>(*cp)) ||
+		*cp == '_' || *cp == '\\')
+		  rc = INTERFACE_IDENTIFIER;
+	    *yy_c_buf_p = save_ch;
+      }
+
+      if (in_module_port_list)
+	    module_port_list_start = false;
       return rc;
   }
 
@@ -906,7 +931,16 @@ TU [munpf]
 `{W} { VLerror(yylloc, "error: Stray tic (`) here. Perhaps you put white "
                        "space between the tic and preprocessor directive?"); }
 
-. { return yytext[0]; }
+. {
+      if (in_module_port_list) {
+	    if (yytext[0] == '(' || yytext[0] == ',')
+		  module_port_list_start = true;
+	    else if (yytext[0] != ')' && yytext[0] != '[' &&
+		     yytext[0] != ']' && yytext[0] != ':')
+		  module_port_list_start = false;
+      }
+      return yytext[0];
+}
 
   /* Final catchall. something got lost or mishandled. */
   /* XXX Should we tell the user something about the lexical state? */
diff --git a/parse.y b/parse.y
index 792454140..aa6fc0a97 100644
--- a/parse.y
+++ b/parse.y
@@ -4781,9 +4781,11 @@ module
         port_declaration_context_init(); }
     module_package_import_list_opt
     module_parameter_port_list_opt
+      { lex_in_module_port_list(true); }
     module_port_list_opt
+      { lex_in_module_port_list(false); }
     module_attribute_foreign ';'
-      { pform_module_set_ports($8); }
+      { pform_module_set_ports($9); }
     timeunits_declaration_opt
       { pform_set_scope_timescale(@2); }
     module_item_list_opt
@@ -4806,16 +4808,16 @@ module
 	}
 	  // Check that program/endprogram and module/endmodule
 	  // keywords match.
-	if ($2 != $15) {
+	if ($2 != $17) {
 	      switch ($2) {
 		  case K_module:
-		    yyerror(@15, "error: module not closed by endmodule.");
+		    yyerror(@17, "error: module not closed by endmodule.");
 		    break;
 		  case K_program:
-		    yyerror(@15, "error: program not closed by endprogram.");
+		    yyerror(@17, "error: program not closed by endprogram.");
 		    break;
 		  case K_interface:
-		    yyerror(@15, "error: interface not closed by endinterface.");
+		    yyerror(@17, "error: interface not closed by endinterface.");
 		    break;
 		  default:
 		    break;
@@ -4831,13 +4833,13 @@ module
 	// module.
 	switch ($2) {
 	    case K_module:
-	      check_end_label(@17, "module", $4, $17);
+	      check_end_label(@19, "module", $4, $19);
 	      break;
 	    case K_program:
-	      check_end_label(@17, "program", $4, $17);
+	      check_end_label(@19, "program", $4, $19);
 	      break;
 	    case K_interface:
-	      check_end_label(@17, "interface", $4, $17);
+	      check_end_label(@19, "interface", $4, $19);
 	      break;
 	    default:
 	      break;
diff --git a/parse_misc.h b/parse_misc.h
index b669a9af0..a9eb7d19b 100644
--- a/parse_misc.h
+++ b/parse_misc.h
@@ -83,6 +83,13 @@ extern UCDriveType uc_drive;
  */
 extern void lex_in_package_scope(PPackage*pkg);
 
+/*
+ * The parser signals when the lexor is scanning a module/interface/program
+ * port list so that ambiguous SystemVerilog interface formals can be
+ * tokenized without depending on declaration order.
+ */
+extern void lex_in_module_port_list(bool flag);
+
 /*
  * Test if this identifier is a type identifier in the current
  * context. The pform code needs to help the lexor here because the